U.S. Pat. No. 5,155,343, "OMNIDIRECTIONAL BAR CODE READER WITH METHOD AND APPARATUS FOR DETECTING AND SCANNING A BAR CODE SYMBOL," discloses a bar code reader which provides for high speed omnidirectional reading of a bar code symbol which may be at a random orientation, distance and relative motion with respect to the reader. The teachings of U.S. Pat. No. 5,155,343 may be used to implement the inventive concepts described and claimed herein, and this patent is therefore hereby incorporated by reference.
Frequently a field containing one bar code symbol may also possibly contain a second bar code symbol which represents information that differs from the information represented by the first bar code symbol. If the locations of either of these two bar code symbols are not known a priori, it can be important to be able to distinguish them so that they may be interpreted properly. This is particularly the case where the symbologies of the two bar code symbols are identical and some indicia other than the information actually encoded must be used to distinguish which of the two types of bar code symbology is used to encode a particular symbol.
One important context in which this problem arises is in the placement of Postnet bar code symbols. While the problem if misplacement and misorientation of a primary Postnet bar code symbol is described in detail in the above-referenced patent applications, it is possible that a so-called computerized forwarding system (CFS) label may also be placed in the same field as the original Postnet bar code symbol. Typically, this will take place if it is determined by a human or machine reading the first bar code symbol that some information concerning the addressee of a piece of mail has changed, necessitating that this information be updated on the piece of mail. One common example occurs when the addressee of a piece of mail moves to a new address. To preserve the efficiency of the Postnet system, this updated information should be placed directly upon the piece of mail.
It is particularly useful if the CFS label is printable by the same method as the original Postnet symbol, for example, by a dot matrix printer. Therefore, it is particularly efficient to use the same kind of symbology for the secondary CFS bar code as is used for the primary Postnet symbol. This requires that an automatic recognition system such as that described in the above-mentioned patent applications can also be used to interpret the information contained in both bar code symbols. It also requires that the automatic recognition system be able to determine which symbol is the primary Postnet symbol and which is the secondary CFS symbol.
The present invention is embodied in a bar code reader in which bar codes are rapidly and reliably read. Furthermore, a bar code reader in accordance with the present invention provides for high speed omnidirectional reading of secondary bar code symbols, which may be at a random orientation, distance and relative motion with respect to the reader.